This reminds me that once where was a store I visited pretty often, almost every single time I entered the store, I would most likely trigger the alarm and nope, I did not carry such tags. The culprit seemed to be the credit cards in my wallet. This article seems to be able the explain what happened. I have to admit the design was both genius and dumb. It's simple, cheap and works most of time but can also easily by passed folding or removing the tag itself altogether. Most annoyingly, high false alarm rate.